For a mobile device connectable to multiple radio communication systems such as a 3G (W-CDMA) system (hereinafter, a 3G) and an LTE system (hereinafter, an LTE), various methods (Inter-RAT mobility) of controlling the mobile device in between the multiple radio communication systems have been specified.
For example, it is specified that when the LTE to which the mobile device has transmitted a connection request has a certain access restriction rejecting acceptance of the connection request, the mobile device executes fallback (CSFB) to a CS domain in the 3G and executes call originating process in the 3G to which the mobile device performs the fallback (see Non-patent Document 1).